The invention relates to the field of measuring instruments, and more particularly to a shock-resistant gage housing for a pressure measuring device such as a sphygmomanometer.
Pressure measuring devices such as sphygmomanometers, which are used to measure the arterial blood pressure of a patent, typically include a pneumatic bulb which inflates a pressure chamber of an attached sleeve that is fitted over a limb (i.e., an arm or a leg) of the patient. A diaphragm or bellows assembly, responsive to changes in fluid pressure of the pneumatic bulb and the sleeve pressure chamber, is positioned in a gage housing which is fluidly connected to the pressure chamber of the sleeve through flexible tubes or hoses. A pointer of a dial indicator is interconnected to the bellows assembly through a movement mechanism which is retained within the gage housing, whereby inflation of the bellows causes corresponding circumferential movement of the pointer enabling a blood pressure measurement procedure to be carried out by a caregiver.
Typically, the above referred to movement mechanisms are quite intricate and complex, and are akin in terms of their manufacture and precision to Swiss watches. For example, and in one such movement mechanism, a pair of diaphragm springs are attached adjacent opposing ends of a spindle. A bottom end of the spindle is placed in contact with the bellows assembly and a twisted bronze band perpendicularly disposed at the top end of the spindle is connected in parallel by a horizontally disposed spring bent part. As the spindle deflects axially in response to the inflation of the bellows, the bent spring part is also caused to deflect, thereby causing the band to twist. The pointer, attached to the bronze band, therefore is caused to rotate in relation to an adjacent dial face.
Devices, such as the foregoing, include numerous moving and relatively complex components, some or each of having numerous bearing surfaces. Therefore, such known devices must be manufactured with relatively strict tolerance margins and significant associated costs in terms of both precision and failure rate in order to minimize errors.
In addition, any adjustments required after assembly of the above mechanisms, such as to null the pointer or adjust the sensitivity of the device, require substantial tear down or at least same undesired disassembly.
Furthermore, discrete and separate elements are typically required within the instrument housing for independently supporting the movement mechanism and the bellows assembly, respectively, and for defining an expansion chamber for the bellows assembly there between.
A more recent and simplified movement mechanism is described in U.S. Pat. No. 5,996,829, incorporated by reference in its entirety. The mechanism includes a vertically disposed axial cartridge having a spirally wrapped ribbon spring with one end mounted to an axially movable elongate shaft and the remaining end of the spring being attached to a fixed tubular sleeve. A bottom portion of the elongate shaft is positioned relative to an expandable diaphragm or bellows, wherein subsequent axial translation of the shaft, caused by movement of the diaphragm, elongates the spirally wound ribbon spring and produces repeatable circumferential movement of a pointer supported at the top end of the shaft. The above movement mechanism is far more lightweight than those previously known due to its simplified construction.
A further advance, described in U.S. Pat. No. 6,168,566, also incorporated by reference in its entirety, permits the design of a housing retaining the movement mechanism described in the ""829 patent to be far more compact.
In spite of the advancements described herein for making pressure measuring devices lighter and less complex in terms of their manufacture, there is still a corresponding need to improve the overall reliability of such devices, particularly with regard to their ability to withstand impact or shock loading. That is to say, if a gage housing for a blood pressure measuring device were to be dropped during use, it is nearly a certainty that the gage housing would be damaged severely enough to prevent further use of the device.
It is a primary object of the present invention to overcome the above-noted deficiencies of the prior art.
It is yet another primary object of the present invention to provide a pressure measuring device which is much more resistant to shock and impact forces than those previously known in the field.
A pressure measuring device, said device comprising:
a housing;
at least one pressure responsive element disposed within said housing;
a movement mechanism having an input end in proximity to a moveable surface of said at least one pressure responsive element;
an indicator connected to an output end of said movement mechanism which indicates changes in pressure; and
shock absorbing means for preventing the transmission of certain shock and impact loads to said device, said shock absorbing means including means for creating a noncontinuous path in order to prevent impinging said shock and input loads from reaching the components contained within the housing.
According to another preferred aspect of the invention, there is provided a pressure measuring device including a housing, said housing retaining a pressure responsive element which is connected to an indicating member that moves relative to a dial face, said device further including a peripheral bumper mounted to said housing, said bumper including an extending portion creating a discontinuous path for a shock or impact load applied to said bumper relative to a movement mechanism retained within said housing.
An advantage of the present invention is that a housing as described herein, such as for use with a blood pressure measuring device, can be dropped or otherwise subjected to shock or impact loads in situations which could be actually encountered during use with minimal damage to the mechanism contained in the housing.
Another advantage of the present invention is that the shock resistant features described herein do not add significant weight to the housing nor detract from the overall reliability or operation of the pressure measuring device.
Yet another advantage of the present invention is that the shock resistant features can easily be manufactured or incorporated into an existing pressure measuring device without significant impacts involving either cost or time.
Still another advantage of the present invention is that other gage housings which can by virtue of an aspect of the present invention be configured for direct connection to a blood pressure sleeve can also include shock resistant features as described herein.
These and other objects, features, and advantages will be more readily apparent to one of ordinary skill in the field from the following Detailed Description which should be read in conjunction with the accompanying drawings.